Rifleshooter.com’s Barrel Length And Velocity Tests

    Following up on their test of 5.56mm and .300 Winchester Magnum ammunition velocities through different barrel lengths, Rifleshooter.com has posted a velocity vs. barrel length examination of .308 Winchester. One of the most well-balanced and versatile .30 caliber rounds in history, the .308 Winchester proved surprisingly well suited to almost all barrel lengths tested, with Winchester 147gr ammunition ranging from almost 3,000 ft/s from a 28″ barrel to just under 2,700 ft/s from a 16.5″ barrel:

    Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph.  At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition.  Average velocity and standard deviation was logged for each round.  Note: I also fired a 30 shots of the IMI Samson 7.62mm 150 grain FMJ with the 28″ and 16.5″ lengths- I’ll discuss why later.  Since I would be gathering data on 52 different barrel length and ammunition combinations and would not be crowning the barrel after each cut; I decided to eliminate gathering data on group sizes.

    Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed.  The barrel was cut off using a cold saw.  The test protocol was repeated for the next length.

    Temperature was 47F.

    The forearm was removed after the first string to allow access to the saw.  Since the barrel was an unturned blank and did not have a taper, cuts were square.

    All shooting was done from a bench, with a Sinclair rest and rear bag.

    Results

    308 Winchester Barrel length in inches versus Muzzle velocity in feet-per-second (ft/sec)Rifleshooter.com
    Barrel length Winchester 147 FMJ IMI Samson 7.62 150 FMJ Federal 168 Gold Medal Winchester 180 PP
    28 2965 2823 2706 2632
    27 2962 2800 2697 2607
    26 2955 2801 2673 2597
    25 2917 2769 2659 2585
    24 2909 2766 2635 2553
    23 2877 2744 2618 2553
    22 2837 2718 2597 2527
    21 2807 2683 2580 2507
    20 2804 2679 2565 2478
    19 2757 2634 2532 2441
    18 2739 2595 2523 2411
    17 2707 2577 2481 2401
    16.5 2682 2561 2466 2373
    AVG velocity loss fps/inch 24.6 22.8 20.9 22.5

    The data presented as a line chart

     

    308 optimum barrel length chart

     

    These sorts of studies can really help readers understand their subjects better. Especially when methodology is recorded meticulously like this, not only are the data helpful for determining ballistics from a rifle of known barrel length, but also what barrel length is right for a certain purpose.

    And just maybe, Rifleshooter’s 16.5″ barrel length results with 147gr ammunition have me taking a second look at that 16.25″ barreled DSA SA 58 at my local gun shop…

    Be sure to follow the link and read the whole thing.

    Nathaniel F

    Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. He can be reached via email at [email protected]


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